Both contracts are for US$3 million.
The 33-year-old Howell pitched for the Tampa Bay Rays from 2006-12, then spent the last four seasons with the Los Angeles Dodgers. He was 1-1 last year with a 4.09 ERA, his highest since 2011. He struck out 44 and walked 15 in 50 2/3 innings.
Howell started his big league career with Kansas City in 2005 and has a 35-29 record with a 3.77 ERA in 33 starts and 498 relief appearances.
Smith split 2016 between the Los Angeles Angels and Chicago Cubs, going 2-5 with a 3.46 earned-run average over 52 innings.
Toronto designated catcher A.J. Jimenez for assigment to make room for Smith on the 40-man roster and desingated left-hander Chad Girodo for Howell’s roster spot.